I recently posted about setting up an (old, white, wireless, bluetooth) apple keyboard.
When I bought this keyboard used, I actually had a problem that I'd had with a previous apple keyboard of the same style. In the past occasion I believe now that I accidentally solved the problem. Now I have found the solution.
The problem is that the space bar is "sticky". When you press it right in the center it works fine but if you hit on either the far right or left side it stays stuck in or at least feels like it's clicking into place rather than smoothly pressing and releasing.
I tried cleaning it and blowing in it to no avail. Finally I figured out what was going on. If you pop off the space bar (just pull it off gently holding both left and right sides), you will see that there is a little metal bar attached underneath. This bar needs to be attached with the long part of the bar hooked into the space bar itself and the two short ends attached to the keyboard. When aligning to attach the space bar to the keyboard, first attach the long part of the bar to the space bar. Hold the space bar so that when it is attached the part where the long bar meets the actual space bar is at the top (far side from you), with the little ends of the bar pointing at you.
Here's a video to explain it better:
